1. Field of the Invention
The present invention relates to a highly efficient encoding method for encoding a digital picture signal and compressing the data amount thereof and a decoding apparatus for decoding the compressed digital picture signal into the original digital picture signal. In particular, the present invention relates to an encoding method for encoding a digital picture signal and transmitting additional information along with the encoded information, a picture encoding apparatus, a picture encoding and transmitting method, a picture recording medium, a picture decoding method, and a picture decoding apparatus.
2. Description of Related Art
FIG. 1 is a block diagram showing an example of a picture signal encoding apparatus that compresses a digital picture signal. The picture signal encoding apparatus shown in FIG. 1 is an encoding apparatus corresponding to an adaptive dynamic range encoding method (hereinafter referred to as the ADRC method). In the ADRC method, an input picture signal is divided into blocks each of which is composed of a predetermined number of pixels. Pixels of each block are adaptively encoded corresponding to the dynamic range of the block. The ADRC method has been proposed by the applicant of the present patent application as U.S. Pat. No. 4,703,352, issued on Oct. 27, 1987. Next, with reference to FIG. 1, the ADRC method will be briefly described. An input picture signal is supplied from an input terminal 1 to a block dividing portion 2. For example, each block composed of nine pixels of 3 pixels.times.3 lines (hereinafter referred to as a block of (3.times.3) pixels) is supplied to a maximum value detecting portion 3 and a minimum value detecting portion 4. The maximum value detecting portion 3 detects the maximum value MAX of the pixel values of the block. The minimum value detecting portion 4 detects the minimum value MIN of the pixel values of the block. The maximum value MAX is supplied from the maximum value detecting portion 3 to a subtracting portion 5. The minimum value MIN is supplied from the minimum value detecting portion 4 to the subtracting portion 5, a subtracting portion 6, and a framing portion 15. The subtracting portion 5 subtracts the minimum value MIN from the maximum value MAX and generates a dynamic range DR. The dynamic range DR is supplied from the subtracting portion 5 to a quantizing step width calculating portion 7 and the framing portion 15. The quantizing step width calculating portion 7 calculates a quantizing step width .DELTA. corresponding to the dynamic range DR supplied from the subtracting portion 5. The calculated quantizing step width .DELTA. is supplied to a quantizing portion 8.
Nine pixels of a block of (3.times.3) pixels are supplied from the input terminal 1 to the subtracting portion 6. By subtracting the minimum value MIN from the pixel values of the nine pixels, these pixel values are normalized. The normalized pixel values are supplied to the quantizing portion 8. The quantizing portion 8 quantizes each of the normalized pixel values with the quantizing step width .DELTA. and supplies the resultant values as quantized values q to the framing portion 15. The framing portion 15 frames the dynamic range DR, the minimum value MIN, and the nine quantized values q and outputs the framed signal as an output signal. The output signal is recorded on a recording medium such as a disc or transmitted through a transmission line.
FIG. 2 is a block diagram showing an example of a picture signal decoding apparatus that decodes a digital picture signal that has been encoded by the ADRC encoding apparatus shown in FIG. 1. A signal reproduced from a recording medium or a signal supplied through a transmission line is supplied from an input terminal 30 to a deframing portion 34. The deframing portion 34 deframes the input signal that has been framed for each block into a dynamic range DR, a minimum value MIN, and nine quantized values q. The deframing portion 34 supplies the dynamic range DR and the quantized values q to a decoding portion 41. In addition, the deframing portion 34 supplies the minimum value MIN to an adding portion 42. The decoding portion 41 dequantizes the nine quantized values q corresponding to the dynamic range DR and supplies the dequantized values to the adding portion 42. The adding portion 42 adds the maximum value MAX to the dequantized values and thereby decodes the nine pixel values of the block of (3.times.3) pixels. The nine decoded pixel values are supplied to a time sequence converting portion 43. The time sequence converting portion 43 converts the decoded pixel values of blocks into pixel values of time sequence.
In the conventional ADRC method, pixel values of each block are quantized with a quantizing step width corresponding to a dynamic range so as to compress pixel values. However, important data that is the minimum value MIN and the dynamic range DR that are transmitted along with compressed pixel values is not compressed, but simply transmitted.
However, each pixel value of a digital picture signal is represented by eight bits that have 256 tones. When each pixel value of eight bits is encoded, the important data of the minimum value MIN and the dynamic range DR is represented by 16 bits per block. In other words, each of the minimum value MIN and the dynamic range DR is represented by eight bits. Thus, in this case, since the important data of the minimum value MIN and the dynamic range DR is not compressed, a high picture compression that has been desired cannot be accomplished.